This invention relates to an apparatus with a fluid sample collection device with one or more sensors for the measurement of analytes in conjunction with a calibration assembly or device. More particularly, the present invention relates to such an apparatus that is a portable collector, sensor and calibrator assembly for use with a measurement display means.
Numerous methods and apparatus exist in the art for measuring chemical components or analytes of fluids. For instance, when the fluid is a liquid or liquid with a dissolved gas with or without the presence of solids, it may be necessary with current technology to transport a sample to a location for testing. With centralized testing, the bulky, stationary, elaborate and sophisticated equipment performs the analysis on a practically endless number of samples. An example of this is the qualitative and/or quantitative measurement of constituents or analytes of blood. For instance, the measurement of blood gases, usually a measure of the partial pressures of oxygen and carbon dioxide, along with the pH from a sample of arterial blood gives the state of the acid base balance of the effectiveness of both the respiratory and cardiovascular systems of the human or vertebrate body. For measuring constituents of blood, the blood sample is drawn from the patient and usually, as in the case of blood gases, transported to a central location for testing.
This technique of transporting the sample to stationary measuring equipment can lead to problems. Ingenious technology has broached solutions to maintain the original composition of the fluid during transportation. Elaborate designs for syringes used in taking the blood samples overcame some of the problems that resulted in inaccurate readings of the particular chemical constituent being measured. For instance, for determining blood gas composition, the problem of air contamination in the collected sample was solved by the use of liquid heparin as an anticoagulant. Unfortunately, this introduced a sample dilution problem. Subsequent development resulted in the use of heparin in the dry state as opposed to the liquid state to avoid this dilution. Also, elaborate designs provide for proper mixing of the sample after transportation and before testing. Even with these improvements, there are many reports in the literature that suggest that the values obtained in the measurement of blood gases depend on the type of measuring equipment and the technique for sample collection.
The art also has attempted to develop more portable measuring equipment rather than the fairly expensive nonportable equipment that engender the elaborate and cumbersome transportation techniques. Portable devices would shorten or overcome transporting the sample altogether so that a patient's blood gases could be measured at the bedside in a manner similar to measuring a patient's temperature. U.S. Pat. Nos. 3,000,805 and 3,497,442 show two such devices. The former has electrodes located on a syringe plunger and the latter has electrodes placed in the syringe well to conduct the measurements. The electrodes are the sensing devices for the blood gases. In the allowed United States patent application Ser. No. 07/343,234, assigned to the same assignee as the present application, the applicants describe and claim a portable blood gas sensor which includes electrodes fabricated from a conventional silk screening process where the electrodes are screened on to a ceramic substance. Typically, these electrodes are used along with an electrolyte and analyte permeable membrane that covers the sensor. Some of these membranes may be hydratable membranes that can be stored in a dry state and hydrated just prior to use.
With any device for detecting and measuring the analytes in fluid, the device must be calibrated in some manner to obtain accurate values for the amounts of the analytes in the fluid. In the larger stationary equipment, calibration occurs through the use of reference fluids that are analyzed before and sometimes during the analysis process of the analyte. Such reference fluids can also be used with portable analyte measuring devices but portable devices should be made as user friendly as possible so their use actually can be more portable.
An object of the present invention is to provide a fluid collection and sensor assembly apparatus that has a calibration device. This gives the advantages of: ready-to-use sensors, and assistance in the generation of results in a more timely, accurate and inexpensive manner.